feat: [FC-0047] xBlock offline mode

[PavloNetrebchuk]

https://www.figma.com/design/iZ56YMjbRMShCCDxqrqRrR/Open-edX-Mobile-App-All-Screens-v2.1?node-id=3240-20123&t=TDhBl4mEV0pNeAEs-0

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• Added a dedicated offline tab for managing user downloaded content.
• Added informational dialogs to provide users with additional context before downloading and to inform them about errors.
• Extended offline functionality to include xBlocks, ensuring that users can interact with and progress through xBlocks content even when offline. This includes saving user progress locally, which will be synced once the user is back online.

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Light Theme	Dark Theme
https://github.com/openedx/openedx-app-android/assets/141041606/3c58b3cf-9f65-492d-94d5-e880ba735a8e	https://github.com/openedx/openedx-app-android/assets/141041606/b19c141c-5364-4f1b-911c-a6cff51db675

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Offline xBlock logic

offline.mp4

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[sdaitzman]

Hi @PavloNetrebchuk, thank you for all your work on this offline xBlock effort. I just wanted to note that the course-level tab title should be Downloads, not Offline. The title varied a lot in earlier design files, but we decided to standardize on Downloads at a mobile design weekly call